Benzoxazinones as inhibitors of HIV reverse transcriptase

ABSTRACT

Certain benzoxazinones are useful in the inhibition of HIV reverse transcriptase (including its resistant varieties), the prevention or treatment of infection by HIV and the treatment of AIDS, either as compounds, pharmaceutically acceptable saks, pharmaceutical composition ingredients, whether or not in combination with other antivirals, immunomodulators, antibiotics or vaccines. Methods of treating AIDS and methods of preventing or treating infection by HIV are also described.

This is a division of application Ser. No. 08/188,005, filed Jan. 28, 1994, which is a continuation-in-part of Merck Case 18793IA, filed Apr. 27, 1993, U.S. Ser. No. 08/054,805, which is a continuation-in-part of Merck Case 18793, filed Aug. 7, 1992, U.S. Ser. No. 07/926,607, both now abandoned.

BACKGROUND OF THE INVENTION

This case is related to Merck Cases 18429, Ser. No. 07/746,445, filed Aug. 16, 1991, now abandoned, 18429IA, Ser. No. 07/880,121, filed Aug. 7, 1992, now abandoned, and 18727.

A retrovirus designated human immunodeficiency virus (HIV) is the etiological agent of the complex disease that includes progressive destruction of the immune system (acquired immune deficiency syndrome; AIDS) and degeneration of the central and peripheral nervous system. This virus was previously known as LAV, HTLV-III, or ARV. A common feature of retrovirus replication is reverse transcription of the RNA genome by a virally encoded reverse transcriptase to generate DNA copies of HIV sequences, a required step in viral replication. It is known that some compounds are reverse transcriptase inhibitors and are effective agents in the treatment of AIDS and similar diseases, e.g., azidothymidine or AZT.

Nucleotide sequencing of HIV shows the presence of a pol gene in one open reading frame [Ratner, L. et al., Nature, 313, 277 (1985)]. Amino acid sequence homology provides evidence that the pol sequence encodes reverse transcriptase, an endonuclease and an HIV protease [Toh, H. et al., EMBO J. 4, 1267 (1985); Power, M. D. et al., Science, 231, 1567 (1986); Pearl, L. H. et al., Nature 329, 351 (1987)].

Applicants demonstrate that the compounds of this invention are inhibitors of HIV reverse transcriptase. The particular advantages of the present compounds are their demonstrated inhibition of resistant HIV reverse transcriptase.

BRIEF DESCRIPTION OF THE INVENTION

Compounds of formula I, as herein defined, are disclosed. These compounds are useful in the inhibition of HIV reverse transcriptase (and its resistant varieties), the prevention of infection by HIV, the treatment of infection by HIV and in the treatment of AIDS and/or ARC, either as compounds, pharmaceutically acceptable salts (when appropriate), pharmaceutical composition ingredients, whether or not in combination with other antivirals, anti-infectives, immunomodulators, antibiotics or vaccines. Methods of treating AIDS, methods of preventing infection by HIV, and methods of treating infection by HIV are also disclosed.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

This invention is concerned with compounds of formula I, combinations thereof, or pharmaceutically acceptable salts thereof, in the inhibition of HIV reverse transcriptase and its resistant varieties, the prevention or treatment of infection by HIV and in the treatment of the resulting acquired immune deficiency syndrome (AIDS). Compounds of formula I are defined as follows: ##STR1## wherein:

X is halo,

X¹ is trihalomethyl, or pentahaloethyl;

Z is O;

R is

(a) C₁₋₈ alkyl, unsubstituted or substituted with A, and A is halo, C₃₋₆ cycloalkyl, CN, hydroxy, C₁₋₄ alkoxy, C₂₋₄ alkynyl-C₁₋₄ alkoxy, aryloxy, C₁₋₄ alkylcarbonyl, nitro, di(C₁₋₂ alkyl)amino, C₁₋₄ alkylamino-C₁₋₂ alkyl, heterocycle, or arylthio;

(b) C₂₋₄ alkenyl, unsubstituted or substituted with

(i) A, or

(ii) aryl, unsubstituted or substituted with A;

(c) C₂₋₅ alkynyl, unsubstituted or substituted with

(i) A, or

(ii) aryl, unsubstituted or substituted with A; or

(d) C₃₋₄ cycloalkyl, unsubstituted or substituted with

(i) A, or

(ii) aryl, unsubstituted or substituted with A,

or pharmaceutically acceptable salt thereof.

This invention also encompasses a pharmaceutical composition useful for inhibiting HIV reverse transcription, comprising an effective amount of a compound of Formula II, ##STR2## and a pharmaceutically acceptable carrier, wherein

X is halo;

X¹ is trihalomethyl; pentahaloethyl; C₂₋₅ alkyl;

C₂₋₅ alkynyl;

C₃₋₅ cycloalky; or aryl;

Z is O or S;

R is

(a) C₁₋₈ alkyl, unsubstituted or substituted with A, and A is halo, C₃₋₆ cycloalkyl, CN,hydroxy, C₁₋₄ alkoxy, C₂₋₄ alkynyl-C₁₋₄ alkoxy, aryloxy, C₁₋₄ alkylcarbonyl, nitro, di(C₁₋₂ alkyl)amino, C₁₋₄ alkylamino-C₁₋₂ alkyl, heterocycle, or arylthio;

(b) C₂₋₄ alkenyl, unsubstimted or substituted with

(i) A, or

(ii) aryl, unsubstituted or substituted with A;

(c) C₂₋₅ alkynyl, unsubstituted or substituted with

(i) A, or

(ii) aryl, unsubstituted or substituted with A; or (d) C₃₋₄ cycloalkyl, unsubstituted or substituted with

(i) A, or

(ii) aryl, unsubstituted or substituted with A,

or pharmaceutically acceptable salt thereof.

Preferred compounds include Compounds 37.2, 4, 2, 5 and 24 of Table I below, in order of descending degree of preference. These compounds have the following structure: ##STR3## (-) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, the most preferred; ##STR4## (-) 6-chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one; ##STR5## (+/-) 6-chloro-4-(2-cyanophenyl)ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one; ##STR6## (+/-) 4-(1-chloro-1,1-difluoromethyl)-4-(2-phenyl-ethynyl)-6-chloro-1,4-dihydro-2H -3,1-benzoxazin-2-one; ##STR7## (+/-) 4-(2-[dimethylaminomethyl]ethynyl)-4-trifiuoromethyl-6-chloro-1,4-dihydro-2H-3,1benzoxazin-2-one;

or a pharmaceutically acceptable salt thereof.

The compounds of the present invention are specifically illustrated in Tables I and II below:

                                      TABLE I                                      __________________________________________________________________________      ##STR8##                                                                                                       IC*.sub.50                                                                           IC*.sub.50                              Compound                                                                             R            X.sup.1 MP(°C.)                                                                       wt    dm     CIC*.sub.95                      __________________________________________________________________________            ##STR9##    CF.sub.3                                                                               186-187.5                                                                            58 nM 4100 nM                                 2                                                                                     ##STR10##   CF.sub.3                                                                               245-246                                                                              25    480    6 nM                             3(+)                                                                                  ##STR11##   CF.sub.3                                                                               178-179                                                                              2900  37,000 >200                             4(-)                                                                                  ##STR12##   CF.sub.3                                                                               "     8.6   69     12                                .sup.+ measured in nM or nanomoles/liter.   -                                 5                                                                                     ##STR13##   CF.sub.2 Cl                                                                            154-155                                                                              12 nM 350 nM                                  6                                                                                     ##STR14##   CF.sub.3                                                                               225-226                                                                              1,700 19,000                                  7                                                                                     ##STR15##   CF.sub.3                                                                               160-161                                                                              91    3,460                                   8                                                                                     ##STR16##   CF.sub.3                                                                               183-184                                                                              163   8,470                                   9                                                                                     ##STR17##   CF.sub.3                                                                               168-171                                                                              83 nM 210 nM                                  10                                                                                    ##STR18##   CF.sub.3                                                                               159-160                                                                              18    390                                     11                                                                                    ##STR19##   CF.sub.3                                                                               185-186                                                                              16    270    6.0 nM                           12(+/-)                                                                               ##STR20##   CF.sub.3                                                                               137-147                                                                              12    280    25                               13                                                                                    ##STR21##   CF.sub.3                                                                               157   390 nM                                                                               10.sup.5 nM                             14                                                                                    ##STR22##   CF.sub.3                                                                               174-176                                                                              130   65,000                                  15                                                                                    ##STR23##   CF.sub.3                                                                               165-166                                                                              29    >10.sup.5                               16                                                                                    ##STR24##   CF.sub.3                                                                               230-240                                                                              1900  1900   78,000                           17                                                                                    ##STR25##   CF.sub.3                                                                               132-133                                                                              2300  >10.sup.5                               18                                                                                    ##STR26##   CF.sub.3                                                                               148-149                                                                              15 nM 2,650 nM                                                                              50 nM                            19                                                                                    ##STR27##   CF.sub.3                                                                               136-137                                                                              24    25,000                                  20                                                                                    ##STR28##   CF.sub.3                                                                               162-164                                                                              145   10.sup.5                                21                                                                                    ##STR29##   CF.sub.3                                                                               145-146                                                                              860   125,000                                 22                                                                                    ##STR30##   "       150-151                                                                              55    3,650                                   23                                                                                    ##STR31##   CF.sub.3                                                                               131-133                                                                              1300 nM>                                                                             30,000 nM                               24                                                                                    ##STR32##   CF.sub.3                                                                               146.5-147.5                                                                          43    1950   100                              25                                                                                    ##STR33##   CF.sub.3                                                                               122-124                                                                              220   >10.sup.5                               26                                                                                    ##STR34##   CF.sub.3                                                                               224-225                                                                              0.24  >10.sup.5                               27                                                                                    ##STR35##   "       203-204                                                                              550   >10.sup.5                               28                                                                                    ##STR36##                                                                                   ##STR37##                                                                             118-120                                                                              307 nM                                                                               114,250 nM                                                                            1500 nM                          29                                                                                    ##STR38##                                                                                   ##STR39##                                                                             166-168                                                                              1,900 >10.sup.5                               30                                                                                    ##STR40##                                                                                   ##STR41##                                                                             100-101.5                                                                            410   3000                                    31                                                                                    ##STR42##                                                                                   ##STR43##                                                                             140.5-141.5                                                                          410   4250                                    32                                                                                    ##STR44##                                                                                   ##STR45##                                                                             172-173                                                                              5400                                          33                                                                                    ##STR46##                                                                                   ##STR47##                                                                             277-278                                                                              300 nM                                        34                                                                                    ##STR48##                                                                                   ##STR49##                                                                             125-126                                                                              16,500                                                                               >300,000 nM                             35                                                                                    ##STR50##                                                                                   ##STR51##                                                                             184-185                                                                              650   >300,000                                36                                                                                    ##STR52##                                                                                   ##STR53##                                                                             151-152                                                                              52    >300,000                                37                                                                                    ##STR54##                                                                                   ##STR55##                                                                             186-187                                                                              5,300 >10.sup.5                               37.2(-)                                                                               ##STR56##                                                                                   ##STR57##    2 nM  85.sup.+  nM                            __________________________________________________________________________      .sup.+ other data on Compound 38 is provided in the Examples section.    

                                      TABLE II                                     __________________________________________________________________________      ##STR58##                                                                                                  IC*.sub.50                                                                          IC*.sub.50                                   Compound                                                                             R         X.sup.1 MP(°C.)                                                                      wt   dm     CIC*.sub.95                           __________________________________________________________________________     38                                                                                    ##STR59##                                                                                ##STR60##                                                                             177-179                                                                             136 nM                                                                              >300,000 nM                                  39                                                                                    ##STR61##                                                                                ##STR62##                                                                             135-136                                                                             510  >300,000 nM                                  40                                                                                    ##STR63##                                                                                ##STR64##                                                                             125-126                                                                             48   29,000                                       41                                                                                    ##STR65##                                                                                ##STR66##   1400 nM                                                                             >300,000 nM                                  42                                                                                    ##STR67##                                                                                ##STR68##                                                                             218-220                                                                             1450                                              43                                                                                    ##STR69##                                                                                ##STR70##                                                                             187-188                                                                             610                                               44                                                                                    ##STR71##                                                                                ##STR72##                                                                             206-207                                                                             15 nM                                                                               >300,000 nM                                                                           100 nM                                45                                                                                    ##STR73##                                                                                ##STR74##                                                                             147-148                                                                             560  >300,000 nM                                  46                                                                                    ##STR75##                                                                                ##STR76##                                                                             186-187                                                                             41   >300,000 nM                                  __________________________________________________________________________

The compounds of the present invention may have asymmetric centers and may occur, except when specifically noted, as racemates, racemic mixtures or as individual diastereomers, or enantiomers, with all isomeric forms being included in the present invention. The term (+/-) is intended to encompass (+) optical isomers or (-) optical isomers or mixtures thereof.

When any variable (e.g., R) occurs more than one time in any constituent or in formula I, its definition on each occurrence is independent of its definition at every other occurrence. Also, combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

As used herein except where noted, "alkyl" is intended to include both branched- and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms; "alkenyl" is intended to cover both branched- and straight chain alkyl groups with at least one carbon-carbon double bond; "alkynyl" is intended to cover both branched- and straight chain alkyl groups with at least one carbon-carbon triple bond. "Halogen" or "halo" as used herein, means fluoro, chloro, bromo and iodo.

As used herein, with exceptions as noted, "aryl" is intended to mean phenyl, naphthyl, tetrahydronaphthyl, biphenyl, phenanthryl, anthryl or acenaphthyl.

The term heterocycle or heterocyclic, as used herein except where noted, represents a stable 5- to 7-membered monocyclic or stable 8- to 11-membered bicyclic heterocyclic ring which is either saturated, partially unsaturated or unsaturated, and which consists of carbon atoms and from one to four heteroatoms selected from the group consisting of N, O and S, and wherein the nitrogen and sulfur heteroatoms may optionally be oxidized, and including any bicyclic group in which any of the above-defined heterocyclic rings is fused to a benzene ring. The heterocyclic ring may be attached at any heteroatom or carbon atom which results in the creation of a stable structure. Examples of such heterocyclic elements include piperidinyl, piperazinyl, 2-oxopiperazinyl, 2-oxopiperidinyl, 2-oxopyrrolidinyl, 2-oxoazepinyl, azepinyl, pyrrolyl, 4-piperidonyl, pyrrolidinyl, pyrazolyl, pyrazolidinyl, imidazolyl, imidazolinyl, imidazolidinyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, oxazolyl, oxazolidinyl, isoxazolyl, isoxazolidinyl, morpholinyl, thiazolyl, thiazolidinyl, isothiazolyl, quinuclidinyl, isothiazolidinyl, indolyl, quinolinyl, isoquinolinyl, benzimidazolyl, thiadiazoyl, benzopyranyl, benzothiazolyl, benzoxazolyl, furyl, tetrahydrofuryl, benzofuranyl, tetrahydropyranyl, thienyl, benzothienyl, thiamorpholinyl, thiamorpholinyl sulfoxide, thiamorpholinyl sulfone, and oxadiazolyl.

The compounds of the present invention can be synthesized by the following methods. ##STR77##

In the synthesis of the benzoxazines of the present invention, the general method typically involves cyclization on a benzene nucleus as a final step. See Scheme I. The amino group of parachloroaniline is first protected with, e.g. pivaloyl chloride, to give 2. Other less preferable amino protecting groups include t-butoxy-carbonyl, acetate or isovaleroyl groups. About 2 equivalents of an alkyllithium are then reacted with 2, preferably n-butyl lithium. No other organo metallic compounds are suitable for this metalation step. Subsequently, reaction with CF₃ COOEt followed by quenching gives 3.

The synthesis of the tertiary carbinol 4 follows, by Grignard addition at the ketone of 3. The Grignard reagent must be a salt of a divalent cation, e.g. Mg⁺⁺ or Zn⁺⁺. Monovalent cations are found unsuitable, such as Li⁺ or Na⁺. Suitable solvents include but are not limited to THF or ether. A wide range of temperature conditions are allowed between about 0° C. and about room temperature.

Ring closure to produce the compounds of the present invention 5 is accomplished with condensing agents such as 1,1'-carbonyldiimidazole, phosgene, dimethylcarbonate, diphenylcarbonate, or di-(paranitrophenyl)carbonate. Cyclization can be accomplished with any of these compounds, as well as a wide variety of others.

A specific instance of Scheme I is provided in Scheme IA. It charts the synthesis of L-741,211, which is a racemate of Compound 37.2, as further provided in Example 6. ##STR78##

Scheme II provides one method for derivatizing acetylene substitutions at the 4-position of the benzoxazine nucleus. By way of illustration, Compound 6 is metalized, then a zinc salt is added. In the Heck reaction the catalyst tetrakis (triphenylphosphine)palladium(0) omplexed with CuI is employed to give 7. ##STR79##

Scheme III illustrates substitution of a 4-acetylene group with an N-containing heterocycle. The Mannich reaction involves a condensation reaction of formaldehyde with the heterocycle, e.g. pyrrolidine. Substitution on the terminal carbon follows in the presence of CuI as catalyst. ##STR80##

Scheme IV illustrates the resolution of optical isomers of the compounds of Formula I or Formula II. In this example, (-) camphanic acid is the resolving agent. A wide variety of other resolving agents are suitable, including O-methyl mandelic acid chloride or Mosher's reagent. It is apparent to the skilled artison how to separate such isomers.

Scheme IVA is specifically adapted to the resolution of L-741,211 in the isolation of L-743,726. See Scheme IVA, and Example 6. ##STR81##

Cyclopropyl acetylene is prepared by Scheme V in accordance with published procedures, e.g. C. E. Hudson et al., J. Am. Chem. Soc. 94, 1158 (1972) and W. Schoberth et al., Synthesis, 703 (1972).

The compounds of this invention are useful in the preparation and execution of screening assays for antiviral compounds. For example, the compounds of this invention are useful for isolating enzyme mutants, which are excellent screening tools for more powerful antiviral compounds. Furthermore, the compounds of this invention are useful in establishing or determining the binding site of other antivirals to HIV reverse transcriptase, e.g., by competitive inhibition. Thus the compounds of this invention are commercial products to be sold for these purposes.

The compounds of the present inventions are useful in the inhibition of HIV reverse transcriptase, the prevention or treatment of infection by human immunodeficiency virus (HIV) and the treatment of consequent pathological conditions such as AIDS. Treating AIDS or preventing or treating infection by HIV is defined as including, but not limited to, treating a wide range of states of HIV infection: AIDS, ARC (AIDS related complex), both symptomatic and asymptomatic, and actual or potential exposure to HIV. For example, the compounds of this invention are useful in treating infection by HIV after suspected past exposure to HIV by e.g., blood transfusion, exchange of body fluids, bites, accidental needle stick, or exposure to patient blood during surgery.

The particular advantage of the compounds of this invention is their potent inhibition against HIV reverse transcriptase rendered resistant to other antivirals, such as L-697,661, which is 3-([(4,7-dichloro-1,3-benzoxazol-2-yl)methyl]-amino)-5-ethyl-6-methyl-pyridin-2(1H)-one; or L-696,229, which is 3-[2-(1,3-benzoxazol-2-yl)ethyl]-5-ethyl-6-methyl-pyridin-2(1H)-one; or AZT.

For these purposes, the compounds of the present invention may be administered orally, parenterally (including subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques), by inhalation spray, or rectally, in dosage unit formulations containing conventional non-toxic pharmaceutically-acceptable carriers, adjuvants and vehicles.

Thus, in accordance with the present invention there is further provided a method of treating and a pharmaceutical composition for treating HIV infection and AIDS. The treatment involves administering to a patient in need of such treatment a pharmaceutical composition comprising a pharmaceutical carder and a therapeutically-effective amount of a compound of the present invention.

These pharmaceutical compositions may be in the form of orally-administrable suspensions or tablets; nasal sprays; sterile injectable preparations, for example, as sterile injectable aqueous or oleagenous suspensions or suppositories.

When administered orally as a suspension, these compositions are prepared according to techniques well-known in the art of pharmaceutical formulation and may contain microcrystalline cellulose for imparting bulk, alginic acid or sodium alginate as a suspending agent, methylcellulose as a viscosity enhancer, and sweeteners/flavoring agents known in the art. As immediate release tablets, these compositions may contain microcrystalline cellulose, dicalcium phosphate, starch, magnesium stearate and lactose and/or other excipients, binders, extenders, disintegrants, diluents and lubricants known in the art.

When administered by nasal aerosol or inhalation, these compositions are prepared according to techniques well-known in the art of pharmaceutical formulation and may be prepared as solutions in saline, employing benzyl alcohol or other suitable preservatives, absorption promoters to enhance bioavailability, fluorocarbons, and/or other solubilizing or dispersing agents known in the art.

The injectable solutions or suspensions may be formulated according to known art, using suitable non-toxic, parenterally-acceptable diluents or solvents, such as mannitol, 1,3-butanediol, water, Ringer's solution or isotonic sodium chloride solution, or suitable dispersing or wetting and suspending agents, such as sterile, bland, fixed oils, including synthetic mono- or diglycerides, and fatty acids, including oleic acid.

When rectally administered in the form of suppositories, these compositions may be prepared by mixing the drug with a suitable non-irritating excipient, such as cocoa butter, synthetic glyceride esters or polyethylene glycols, which are solid at ordinary temperatures, but liquidify and/or dissolve in the rectal cavity to release the drug.

The compounds of this invention can be administered orally to humans in a dosage range of 1 to 100 mg/kg body weight in divided doses. One preferred dosage range is 0.1 to 10 mg/kg body weight orally in divided doses. Mother preferred dosage range is 0.1 to 20 mg/kg body weight orally in divided doses. For combination therapy with nucleoside analogs, a preferred dosage range is 0.1 to 20 mg/kg body weight for the compounds of this invention administered orally in divided doses, and 50 mg to 5 g/kg body weight for nucleoside analogs administered orally in divided doses. It will be understood, however, that the specific dose level and frequency of dosage for any particular patient may be varied and will depend upon a variety of factors including the activity of the specific compound employed, the metabolic stability and length of action of that compound, the age, body weight, general health, sex, diet, mode and time of administration, rate of excretion, drug combination, the severity of the particular condition, and the host undergoing therapy.

The present invention is also directed to combinations of the HIV reverse transcriptase inhibitor compounds with one or more agents useful in the treatment of AIDS. For example, the compounds of this invention may be effectively administered, whether at periods of pre-exposure and/or post-exposure, in combination with effective amounts of the AIDS antivirals, immunomodulators, antiinfectives, or vaccines, such as those in the following Table.

                  TABLE                                                            ______________________________________                                         Drug Name   Manufacturer  Indication                                           ______________________________________                                         ANTIVIRALS                                                                     AL-721      Ethigen       ARC, PGL                                                         (Los Angeles, CA)                                                                            HIV positive, AIDS                                   Recombinant Triton Biosciences                                                                           AIDS, Kaposi's                                       Human Interferon                                                                           (Almeda, CA)  sarcoma, ARC                                         Beta                                                                           Acemannan   Carrington Labs                                                                              ARC (See also                                                    (Irving, TX)  immunomodulators)                                    Cytovene    Syntex        sight threatening                                                              CMV                                                  Ganciclovir (Palo Alto, CA)                                                                              peripheral CMV                                                                 retinitis                                            d4T         Bristol-Myers AIDS, ARC                                            Didehydrodeoxy-                                                                            (New York, NY)                                                     thymidine                                                                      ddI         Bristol-Myers AIDS, ARC                                            Dideoxyinosine                                                                             (New York, NY)                                                     EL10        Elan Corp, PLC                                                                               HIV infection                                                    (Gainesville, GA)                                                                            (See also                                                                      immunomodulators)                                    Trisodium   Astra Pharm.  CMV retinitis, HIV                                   Phosphonoformate                                                                           Products, Inc.                                                                               infection, other CMV                                             (Westborough, MA)                                                                            infections                                           Dideoxycytidine;                                                                           Hoffman-La Roche                                                                             AIDS, ARC                                            ddC         (Nutley, NJ)                                                       Novapren    Novaferon Labs,                                                                              HIV inhibitor                                                    Inc. (Akron, OH)                                                               Diapren, Inc.                                                                  (Roseville, MN,                                                                marketer)                                                          Peptide T   Peninsula Labs                                                                               AIDS                                                 Octapeptide (Belmont, CA)                                                      Sequence                                                                       Zidovudine; AZT                                                                            Burroughs     AIDS, adv, ARC                                                   Wellcome (Rsch.                                                                              pediatric AIDS,                                                  Triangle Park, NC)                                                                           Kaposi's sarcoma,                                                              asymptomatic HIV                                                               infection, less severe                                                         HIV disease,                                                                   neurological                                                                   involvement, in                                                                combination with                                                               therapies.                                           Ansamycin LM 427                                                                           Adria Laboratories                                                                           ARC                                                              (Dublin, OH)                                                                   Erbamont                                                                       (Stamford, CT)                                                     Dextran Sulfate                                                                            Ueno Fine Chem.                                                                              AIDS, ARC, HIV                                                   Ind. Ltd.     positive asymptomatic                                            (Osaka, Japan)                                                     Virazole    Viratek/ICN   asymptomatic HIV                                     Ribavirin   (Costa Mesa, CA)                                                                             positive, LAS, ARC                                   Alpha Interferon                                                                           Burroughs     Kaposi's sarcoma,                                                Wellcome (Rsch.                                                                              HIV in combination                                               Triangle Park, NC)                                                                           w/Retrovir                                           Acyclovir   Burroughs     AIDS, ARC,                                                       Wellcome      asymptomatic HIV                                                               positive, in                                                                   combination with                                                               AZT.                                                 Antibody which                                                                             Advanced      AIDS, ARC                                            neutralizes pH                                                                             Biotherapy                                                         labile alpha                                                                               Concepts                                                           aberrant Interferon                                                                        Rockville, MD)                                                     in an immuno-                                                                  adsorption column                                                              L-697,661   Merck (Rahway,                                                                               AIDS, ARC,                                                       NJ)           asymptomatic HIV                                                               positive, also in                                                              combination with                                                               AZT.                                                 L-696,229   Merck         AIDS, ARC,                                                       (Rahway, NJ)  asymptomatic HIV                                                               positive, also in                                                              combination with                                                               AZT.                                                 L-735,524   Merck (Rahway,                                                                               AIDS, ARC,                                                       NJ)           asymptomatic HIV                                                               positive, also in                                                              combination with                                                               AZT.                                                 IMMUNO-MODULATORS                                                              AS-101      Wyeth-Ayerst Labs.                                                                           AIDS                                                             (Philadelphia, PA)                                                 Bropirimine Upjohn        advanced AIDS                                                    (Kalamazoo, MI)                                                    Acemaman    Carrington Labs,                                                                             AIDS, ARC                                                        Inc. (Irving, TX)                                                                            (See also antivirals)                                CL246,738   American Cyanamid                                                                            AIDS, Kaposi's                                                   (Pearl River, NY)                                                                            sarcoma                                                          Lederle Labs                                                                   (Wayne, NJ)                                                        EL10        Elan Corp, PLC                                                                               HIV infection                                                    (Gainesville, GA)                                                                            (See also antivirals)                                Gamma Interferon                                                                           Genentech     ARC, in combination                                              (S. San Francisco,                                                                           w/TNF (tumor                                                     CA)           necrosis factor)                                     Granulocyte Genetics Institute                                                                           AIDS                                                 Macrophage Colony                                                                          (Cambridge, MA)                                                    Stimulating Factor                                                                         Sandoz                                                                         (East Hanover, NJ)                                                 Granulocyte Hoeschst-Roussel                                                                             AIDS                                                 Macrophage Colony                                                                          (Somerville, NJ)                                                   Stimulating Factor                                                                         Immunex (Seattle,                                                              WA)                                                                Granulocyte Schering-Plough                                                                              AIDS                                                 Macrophage Colony                                                                          (Madison, NJ)                                                      Stimulating Factor        AIDS, in combination                                                           w/AZT                                                HIV Core Particle                                                                          Rorer         seropositive HIV                                     Immunostimulant                                                                            (Ft. Washington,                                                               PA)                                                                IL-2        Hoffman-La Roche                                                                             AIDS, ARC, HIV, in                                   Interleukin-2                                                                              (Nutley, NJ)  combination w/AZT                                                Immunex                                                            Immune Globulin                                                                            Cutter Biological                                                                            pediatric AIDS, in                                   Intravenous (Berkeley, CA)                                                                               combination w/AZT                                    (human)                                                                        IMREG-1     Imreg         AIDS, Kaposi's                                                   New Orleans, LA)                                                                             sarcoma, ARC, PGL                                    IMREG-2     Imreg         AIDS, Kaposi's                                                   (New Orleans, LA)                                                                            sarcoma, ARC, PGL                                    Imuthiol Diethyl                                                                           Merieux Institute                                                                            AIDS, ARC                                            Dithio Carbamate                                                                           (Miami, FL)                                                        Alpha-2     Scheming Plough                                                                              Kaposi's sarcoma                                     Interferon  (Madison, NJ) w/AZT: AIDS                                          Methionine- TNI Pharmaceutical                                                                           AIDS, ARC                                            Enkephalin  (Chicago, IL)                                                      MTP-PE      Ciba-Geigy Corp.                                                                             Kaposi's sarcoma                                     Muramyl-Tripeptide                                                                         (Summit, NJ)                                                       Granulocyte Amgen         AIDS, in combination                                 Colony Stimulating                                                                         (Thousand Oaks,                                                                              w/AZT                                                Factor      CA)                                                                rCD4        Genentech     AIDS, ARC                                            Recombinant (S. San Francisco,                                                 Soluble Human                                                                              CA)                                                                CD4                                                                            Rocombinant Biogen        AIDS, ARC                                            Soluble Human                                                                              (Cambridge, MA)                                                    CD4                                                                            Interferon  Hoffman-La Roche                                                                             Kaposi's sarcoma                                     Alfa 2a     (Nutley, NJ)  AIDS, ARC, in                                                                  combination w/AZT                                    SK&F106528  Smith, Kline &                                                                               HIV infection                                        Soluble T4  French Laboratories                                                            (Philadelphia, PA)                                                 Thymopentin Immunobiology HIV infection                                                    Research Institute                                                             (Annandale, NJ)                                                    Tumor Necrosis                                                                             Genentech     ARC, in combination                                  Factor; TNF (S. San Francisco,                                                                           w/gamma Interferon                                               CA)                                                                ANTI-INFECTIVES                                                                Clindamycin with                                                                           Upjohn        PCP                                                  Primaquine  (Kalamazoo, MI)                                                    Fluconazolec                                                                               Pfizer        cryptococcal                                                     (New York, NY)                                                                               meningitis, candidiasis                              Pastille    Squibb Corp   prevention of oral                                   Nystatin Pastille                                                                          (Princeton, NJ)                                                                              candidiasis                                          Ornidyl     Merrell Dow   PCP                                                  Eflornithine                                                                               (Cincinnati, OH)                                                   Pentamidine LyphoMed      PCP treatment                                        Isethionate (Rosemont, IL)                                                     (IM & IV)                                                                      Piritrexim  Burroughs     PCP treatment                                                    Wellcome (Rsch.                                                                Triangle Park, NC)                                                 Pentamidine Fisons Corporation                                                                           PCP prophylaxis                                      isethionate for                                                                            (Bedford, MA)                                                      inhalation                                                                     Spiramycin  Rhone-Poulenc cryptosporidial                                                  Pharmaceuticals                                                                              diarrhea                                                         (Princeton, NJ)                                                    Intraconazole-                                                                             Janssen Pharm.                                                                               histoplasmosis;                                      R51211      (Piscataway, NJ.)                                                                            cryptococcal                                                                   meningitis                                           Trimetrexate                                                                               Warner-Lambert                                                                               PCP                                                  OTHER                                                                          Recombinant Ortho Pharm. Corp.                                                                           severe anemia assoc.                                 Human       (Raritan, NJ) with AZT therapy                                     Erythropoietin                                                                 Megestrol Acetate                                                                          Bristol-Myers treatment of anorexia                                            (New York, NY)                                                                               assoc. w/AIDS                                        Total Enteral                                                                              Norwich Eaton diarrhea and                                         Nutrition   Pharmaceuticals                                                                              malabsorption related                                            (Norwich, NY) to AIDS                                              ______________________________________                                    

It will be understood that the scope of combinations of the compounds of this invention with AIDS antivirals, immunomodulators, anti-infectives or vaccines is not limited to the list in the above Table, but includes in principle any combination with any pharmaceutical composition useful for the treatment of AIDS. For example, a compound of Formula I or Formula II may be suitably administered in combination with a nucleoside analog having known biological activity against HIV reverse transcriptase. Appropriate nucleoside analogs are generally chain terminators and include AZT, ddC, ddI, D4T, HEPT and 3'-fluoro-2',3'-dideoxythymidine.

AZT is synthesized by the methods of J. P. Horwitz et al., J. Org. Chem. 29, 2076 (1964); R. P. Glinski et al., J. Org. Chem. 38, 4299 (1973); C. K. Chu et al., Tetrahedron Letters 29, 5349 (1988). Application of AZT as a therapeutic drug in the treatment of AIDS is disclosed in U.S. Pat. No. 4,724,232.

The compound ddC is synthesized by the methods of J. P. Horwitz et al., J. Org. Chem. 32, 817 (1967); R. Marumoto, Chem. Pharm. Bull. 22, 128 (1974); and T.-S. Lin et al., J. Med. Chem. 30, 440 (1987).

D4T is synthesized by the methods of Herdewijn, P. et al., J. Med. Chem. 30, 1270 (1987).

HEPT is synthesized by the methods of Miyasaka, T. et. al. J. Med. Chem. 32, 2507 (1989); and A. Rosowsky, J. Med. Chem. 24, 1177 (1981). The synthesis of ddC, ddI and AZT are also described in EPO 484071.

The compound 3'-fluoro-2',3'-dideoxythymidine is synthesized by the procedures of Herdewijn, P. et al., J. Med. Chem. 30, 1270 (1987). The compound L-735,524 is N-(2(R)-hydroxy-1(S)-indanyl)-2(R)-phenylmethyl-4-(S)-hydroxy-5-(1-(4-(3-pyridylmethyl)-2(S)-N'-(t-butylcarbamoyl)-piperazinyl))-pentaneamide, or pharmaceutically acceptable salt thereof. L-697,661 or `661` is 3-([4,7-dichloro-1,3-benzoxazol-2-yl)methyl]-amino)-5-ethyl-ethyl-6-methyl-pyridin-2(1H)-one; L-696,229 is 3-[2-(1,3-benzoxazol-2-yl)-ethyl]-5-ethyl-6-methyl-pyridin-2(1H)-one. The synthesis of L-697,661 and L-696,229 is described in EPO 484071, and EPO 462800, both herein incorporated by reference. L-735,524 is synthesized by the methods of EP 0541168, herein incorporated by reference for these purposes.

Preferred combinations are simultaneous, intermittent, or alternating treatments of L-743,726 with or without an inhibitor of HIV protease. An optional third component in the combination is a nucleoside inhibitor of HIV reverse transcriptase, such as AZT, ddC or ddI. A preferred inhibitor of HIV protease is L-735,524. Other preferred inhibitors of HIV reverse transcriptase include L-697,661. These combinations may have synergistic effects on limiting the spread of HIV. Preferred combinations include the following: (1) L-743,726 with L-735,524, and, optionally any of L-697,661, AZT, ddI or ddC; (2) L-743,726 and any of L-697,661, AZT, ddI or ddC. Pharmaceutically acceptable salts of these combinations are also included.

EXAMPLE 1 (+/-) 4-(1,1,1,-trifluoromethyl)-4-(1-buten-4-yl) -6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one; (Compound 15)

Step A: N-(4-chlorophenyl)-2,2-dimethylpropanamide

To a 5L 3 necked round bottomed flask with an overhead stirrer was added 4-chloroaniline (127.57 g, 1 mole), 1200 mL of CHCl₃, and 1200 mL of saturated aqueous Na₂ CO₃ solution. An addition funnel was attached to the flask and charged with 2,2-dimethylpropanoyl chloride (129 mL, 1.05 mole). The acid chloride was added dropwise to the vigorously stirred mixture over 1 h. The resulting mixture was stirred at ambient temperature for an additional 23 h. Some of the product separated from the mixture as white crystals. These crystals were collected by filtration. The filtrate was transferred to a separatory funnel and the layers were separated. The chloroform layer was washed with water and brine. Drying (MgSO₄), filtration, and removal of the solvent in vacuo gave additional product. The two portions of product were combined and recrystallized from boiling EtOAc-hexanes to give 185.6 g of N-(4-chlorophenyl)-2,2-dimethyl propanamide as a white crystalline solid.

Step B 1-(2-amino-5-chlorophenyl)-2,2,2-trifluoroethanone

To an oven dried, 3 L, 3 necked round bottomed flask with an overhead stirrer, argon inlet, and a 500 mL oven dried addition funnel was added N-(4-chlorophenyl)-2,2-dimethylpropanamide (100 g, 472 mmol) and dry THF (1 L). This solution was cooled in an ice bath to 0° C. and the addition funnel was charged with n-butyllithium (387 mL of a 2.5M solution in hexanes, 968 mmol). The n-butyllithium solution was added dropwise to the amide solution slowly over 1 h, maintaining the temperature below +5° C. The resulting solution was aged at 0° C. for 1 h during which time an orange precipitate formed. To this mixture was added ethyl 1,1,1-trifluoroacetate (115 mL, 968 mmol), dropwise over 1 h. The resulting clear solution was aged an additional 30 min. The reaction was quenched with 5% aqueous HCl. The mixture was diluted with 1 L of EtOAc and the layers were separated. The organic phase was washed with brine, dried (MgSO₄), filtered and concentrated in vacuo, to give 160 g of a yellow oil. This material was suspended in 1 L of 3N aqueous HCl and the solution was heated at reflux for 24 h. The cooled solution was diluted with 1 L of EtOAc and the mixture was made basic with concentrated NH₄ OH. The layers were separated and the organic phase was washed with brine, dried (MgSO₄), filtered, concentrated in vacuo, and chromatographed on 1.5 kg of silica gel using 15% EtOAc in hexane as eluant. The chromatographed material was recrystallized from boiling hexane to give 57 g (54%) of pure 1-(2-amino-5-chlorophenyl)-2,2,2-trifluoroethanone as bright yellow crystals, mp: 91°-92° C. ¹ H NMR (CDCl₃): δ6.46 (br s, 2H), 6.69 (d, 1H, J=9.2 Hz), 7.32 (dd, 1H, J=2.4, 9.2 Hz), 7.70 (d, 1H, J=2.4 Hz).

Step C (+/-) 2-(2-Amino-5-chlorophenyl)-1,1,1-trifluoro-5-hexen-2-ol

To a 300 mL oven dried 3 necked, round bottomed flask with a stirring bar, argon inlet, addition funnel and a reflux condenser was added magnesium (turnings, 3.03 g, 125 mmol) and dry THF (75 mL). To this well stirred mixture was added 4-bromo-1-butene (12.0 mL, 118.21 mmol) at such a rate as to maintain a gentle reflux. When the addition was complete, the mixture was aged 30 min then cooled to 0° C. in an ice bath. To this well stirred solution was added a solution of 1-(2-amino-5-chlorophenyl)-2,2,2-trifluoroethanone (5.00 g, 22.36 mmol) in THF (35 mL), dropwise over 30 min. The cooling bath was allowed to expire and the mixture was stirred 20 h at ambient temperature. The reaction was diluted with EtOAc and 10% aqueous citric acid. This mixture was stirred for 4 h. The layers were separated and the organic phase was washed with aqueous NaHCO₃ and brine. Drying (MgSO₄), filtration, removal of the solvent in vacuo, and chromatography on 300 g of silica gel using 15% EtOAc in hexane as eluantas eluant gave 4.80 g of (+/-) 2-(2-amino-5-chlorophenyl)-1,1,1-trifluoro-5-hexen-2-ol as a yellow solid.

Step D (+/-) 4-(1,1,1,-trifluoromethyl)-4-(1-buten-4-yl)-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one

To a 200 mL round bottomed flask with a stirring bar, argon inlet and a reflux condenser was added. (+/-) 2-(2-Amino-5-chlorophenyl)-1,1,1-trifluoro-5-hexen-2-ol (4.80 g, 17.16 mmol), 1,1 '-carbonyldiimidazole (13.91 g, 85.81 mmol) and dry THF (75 mL). This mixture was heated at 60° C. for 18 h. The cooled reaction mixture was diluted with EtOAc and washed with H₂ O (3×200 mL) and brine (250 mL). Drying (MgSO₄), filtration, removal of the solvent in vacuo, followed by recrystallization from boiling EtOAc-hexane gave 3.22g of (+/-) 4-(1,1,1-trifluoromethyl)-4(1 -buten-4-yl)-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one as a white crystalline solid, mp: 165°-166° C. ¹ H NMR (CDCl₃): δ1.99 (m, 1H), 2.09-2.40 (m, 3H), 5.00 (d, 1H, J=1.4 Hz), 5.03 (dd, 1H, J=1.4, 7.9), 5.78 (m, 1H), 6.85 (d, 1H, J=8.6 Hz), 7.21 (br s, 1H), 7.35 (dd, 1H, J=2.2, 8.6 Hz), 9.63 (br s, 1H).

EXAMPLE 2 (+/-) 6-Chloro-4-ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 26) Step A 2-(2-amino-5-chlorophenyl)-1,1,1-trifluoro-3-butyn-2-ol

A 500 ml 3-neck round bottom flask fitted with an addition funnel, argon inlet, stirring bar and digital thermometer was charged with ethynyl magnesium bromide (0.5M in hexane; 268 mL, 134 mmol) then chilled to -78° C. Dropwise addition of a solution of 1-(2-amino-5-chlorophenyl)-2,2,2-trifluororethanone (6.0 g, 26.8 mmoI) in 50 mL THF was completed after 15 minutes keeping the temperature <-55° C. The reaction mixture was stirred for 16 h after slowly warming to room temperature. The dark red solution was quenched at -5° C. by dropwise addition of saturated aqueous ammonium chloride solution (60 mL). Ethyl acetate extraction followed by washes of 10% citric acid, saturated sodium bicarbonate, water and brine afforded 8.5 g crude product after drying over sodium sulfate, filtration, and evaporation of solvent. Purification via flash chromatography using 15-20% ethyl acetate: hexane afforded pure 2-(2-amino-5-chlorophenyl)-1,1,1-trifluoro-3-butyn-2-ol (5 g light brown oil, 75% yield).

Step B (+/-) 6-Chloro-4-ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one

A THF solution of 2-(2-amino-5-chlorophenyl)-1,1,1-trifluoro-3-butyn-2-ol (5.0 g, 20.0 mmol in 225 mL THF) was treated with 1,1'-carbonyldiimidazole (13.0 g, 80.0 mmol) and heated in an oil bath at 60° C. for 17 h. The THF was removed in yacuo, the residue dissolved in ethyl acetate then washed with 10% citric acid, sodium bicarbonate, water and brine before drying over sodium sulfate. Following filtration and evaporation in vacuo the crude product was isolated (3.6 g) and recrystallized from ethyl acetate: hexane. The product (+/-) 6-chloro-4-ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one was isolated as a white crystalline solid (3.22 g, 58.4% yield): mp 226°-227° C. ¹ H-NMR (CDCl₃ +trace DMSO): δ3.16 (s, 1H), 6.98 (d, J=3.3 Hz, 1H), 7.35 (m, 1H), 7.51 (s, 1H), 10.66 (s, 1H).

EXAMPLE 3 (+/-) 6-Chloro-4-(1,1,1-trifluoromethyl)-4-[(3-(1-pyrrolidinyl))-1-propynyl]-1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 7)

A dioxane solution of (+/-)6-chloro-4-ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one (150 mg, 0.544 mmol), pyrrolidine (52.2 μL, 0.626 mmol), paraformaldehyde (20.5 mg, 0.681 mmol), acetic acid (31.1 μL, 0.544 mmol) and copper (I) chloride (20.5 mg, 0.207 mmol in 3.5 ml dioxane) was heated to 50° C. in an oil bath for approximately 2 h. The reaction mixture was quenched into 2N HCl and extracted with ethyl acetate. The aqueous layer was neutralized with solid potassium carbonate and extracted with ethyl acetate (3x). The combined extracts were washed with water and brine before drying over sodium sulfate to afford 140 mg crude product. Chromatographic purification on silica gel and recrystallization from ethyl acetate: hexane afforded crystalline (+/-) 6-chloro-4-(1,1,1-trifluoromethyl)-4-[(3-(1-pyrrolidinyl))-1-propynyl]-1,4-dihydro-2H-3,1-benzoxazin-2-one (89 mg, 46% yield): MP 160°-161° C. (dec). ¹ H-NMR (CDCl₃): δ1.85-1.89 (m, 4H), 2.68-2.71 (m, 4H), 3.67 (s, 1H), 6.88 (d, J=8.55 Hz, 1H), 7.40 (dd, J=2.19, 8.54 Hz, 1H), 7.55 (s, 1H), 9.45 (s, 1H).

(+/-) 6-Chloro-4-(2-cyanophenyl)ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 2)

A solution of 6-Chloro-4-ethynyl-4-(1,1,1-trifluoro-methyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one (138 mg, 0.5 mmol) in 3 mL of dry THF was stirred at -78° C. To this solution was added 0.4 mL (1.0 mmol) of n-butyllithium, 2.5M in hexane. The anion was aged for 10 minutes at -78° C. then 1 mL of ZnCl₂ (1M in ether) solution was added. The reaction mixture was allowed to stir at -78° C. for 15 minutes, the ice bath was removed and the mixture slowly warmed to 0° C. over 30 min. To the reaction mixture was added a solution of 2-iodobenzonitrile (149 mg, 0.65 mmol) in 2 mL THF, followed by tetrakis(triphenylphosphine)palladium(0) (56 mg, 0.05 mmol). The reaction was allowed to warm to r.t. and continued to stir over 15 hours. The reaction mixture was quenched with 10 mL of 2N HCl, extracted with 2×200 mL EtOAc and the combined extracts were washed with H₂ O, brine and dried over MgSO₄. The solvent was removed to give 195 mg of an oil which was flashed chromatographed on silica gel (20% EtOAc in hexane) to afford 60 mg of the unreacted starting material and 35 mg of the coupled product. The latter was triturated with ether to yield 25 mg of (+/-) 6-Chloro-4-(2-cyanophenyl)ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro -2H -3,1-benzoxazin-2-one. mp: 245°-246° C. FAB. MS M+1=377 m/e. ¹ H NMR (CDCl₃): δ6.82-6.85 (d, J=8.5 Hz, 1H); 7.40-7.44 (dd, J=2.1, 8.5 Hz, 1H); 7.56-7.79 (m, 5H); 8.00 (s, 1H).

EXAMPLE 4 (+/-) 4-(1-Chloro-1,1-difluoromethyl)-4-(2-phenylethynyl)-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 5) Step A 1-(2-amino-5-chlorophenyl)-2-chloro-2,2-difluoroethanone

To an oven dried, 300 mL, 3 necked round bottomed flask with a magnetic stirring bar, argon inlet, and a 100 mL oven dried addition funnel was added N-(4-chlorophenyl)-2,2-dimethyl-propanamide (10 g, 47.2 mmol) and dry THF (100 mL). This solution was cooled in an ice bath to 0° C. and the addition funnel was charged with n-butyllithium (38.7 mL of a 2.5M solution in hexanes, 96.8 mmol). The n-butyllithium solution was added dropwise to the amide solution slowly over 1 h, maintaining the temperature below +5° C. The resulting solution was aged at 0° C. for 1 h during which time an orange precipitate formed. To this mixture was added ethyl 1-chloro-1,1-difluoroacetate (10.2 mL, 96.8 mmol), dropwise over 15 min. The resulting clear solution was aged an additional 30 min. The reaction was quenched with 5% aqueous HCl. The mixture was diluted with 1 L of EtOAc and the layers were separated. The organic phase was washed with brine, dried (MgSO₄), filtered and concentrated in vacuo, to give 160 g of a yellow oil. This material was suspended in 200 mL of 3N aqueous HCl and the solution was heated at reflux for 24 h. The cooled solution was diluted with 500 mL of EtOAc and the mixture was made basic with concentrated NH₄ OH. The layers were separated and the organic phase was washed with brine, dried (MgSO₄), filtered, concentrated in vacuo, and chromatographed on 350 g of silica gel using 15% EtOAc in hexane as eluant. The chromatographed material was recrystallized from boiling hexane to give 5.5 g of pure 1-(2-amino-5-chlorophenyl)-2-chloro-2,2-difluoroethanone as bright yellow crystals, mp: 55°-56° C. ¹ H NMR (CDCl₃): δ6.43 (br s, 2H), 6.69 (d, 1H, J=9.0 Hz), 7.31 (dd, 1H, J=2.4, 9.0 Hz), 7.80 (d, 1H, J=2.4 Hz).

Step B (+/-) 2-(2-amino-5-chlorophenyl)-4-phenyl-1-chloro-1,1-difluoro-3-butyn-2-ol

To a 100 mL, 3 necked, oven dried round bottomed flask, with a stirring bar, argon inlet, reflux condenser, and a septum was added ethynyl benzene (2.13 g, 20.83 mmol), dry THF (50 mL) and ethyl magnesium bromide (6.94 mL of a 3.0M solution in ether). This mixture was aged 2 h at ambient temperature then a solution of 1-(2-amino-5-chlorophenyl)-2-chloro-2,2-difluoroethanone (1.00 g, 4.17 mmol) in THF (6 mL) was added with a syringe. The resulting orange-red solution was stirred at ambient temperature for 21.5 h. The reaction was quenched by addition of 1N HCl (50 mL) then diluted with EtOAc. The solution was then made basic with concentrated NH₄ OH and the layers were separated. The organic phase was washed with water and brine. Drying (MgSO₄), filtration, removal of the solvent in vacuo, and chromatography on silica gel using 20% EtOAc in hexane as eluant gave 1.02 g of (+/-) 2-(2-amino-5-chlorophenyl)-4-phenyl-1-chloro-1,1-difluoro-3-butyn-2-ol as an off white solid. ¹ H NMR (CDCl₃): δ4.42 (br s, 2H), 5.10 (br s, 1H), 6.65 (d, 1H, J=8.5 Hz), 7.15 (dd, 1H, J=2.4, 8.5 Hz), 7.38 (m, 3H), 7.55 (m, 2H), 7.70 (d, J=2.4 Hz).

Step C (+/-) 4-(1-Chloro-1,1-difluoromethyl)-4-(2-phenyl-ethynyl)-6-chloro-1,4-dihydro-2H-3, 1-benzoxazin-2-one

To a 100 mL round bottomed flask with a stirring bar, reflux condenser, and an argon inlet was added (+/-) 2-(2-amino-5-chlorophenyl)-4-phenyl-1-chloro-1,1-difluoro-3-butyn-2-ol (0.81 g, 2.37 mmol), dry THF (25 mL), and 1,1'-carbonyldiimidazole (1.919 g, 11.84 mmol). This solution was heated at 60° C. for 20 h. The cooled reaction mixture was diluted with EtOAc and washed with 0.5N HCl, H₂ O, and brine. Drying (MgSO₄), filtration, and removal of the solvent in vacuo gave 890 mg of an oil. This material was chromatographed on 80 g of silica gel using 20% EtOAc in hexane as eluant. The chromatographed material was recrystallized from boiling EtOAc-hexanes to give 507 mg, (58%) of (+/-) 4-(1-chloro-1,1-difluoromethyl)-4-(2-phenylethynyl)-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one as white needles, mp: 154°-155° C. ¹ H NMR (CDCl₃): δ6.89 (d, 1H, J=8.4 Hz), 7.35-7.48 (m, 4H), 7.56 (m,2H), 7.64 (br s, 1H), 9.19 (br s, 1H).

EXAMPLE 5 (-)6-Chloro-4-phenylethynyl-4-trifluoromethyl,1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 4) Step A 2-(2-Amino-5-chlorophenyl)-4-phenyl-1,1,1-trifluoro-3-butyn-2-ol

A solution of lithio phenylacetylide, prepared from 4.83 mL of phenylacetylene (0.044 mol) and 17.2 mL of a 2.5N solution of n-butyllithium in hexane (0.043 mol) in 50 mL of THF at -78° C., was treated with 11.4 g of magnesium bromide etherate (0.044 mol) over 5 minutes. The mixture was allowed to warm to -20° C. and stirring under argon was continued for 30 minutes. The mixture was then cooled to -60° C. and a solution containing 2.5 g (0.011 mol) of 1-(2-amino-5-chloro)-2,2,2-trifluoromethylethanone, previously complexed with an equivalent (2.8 g, 0.011 mol) of magnesium bromide etherate in 25 mL of THF, was added. The reaction mixture was allowed to stir at 15° for one hour before being cooled to 0° C. and treated dropwise with a mixture of 30 mL each of saturated aqueous ammonium chloride solution and water. The mixture was extracted with 2×100 mL portions of ethyl ether, the combined organic phases were washed with brine and dried over MgSO₄. Removal of the drying agent and solvents left 6 g of an oil which was flash chromatographed on silica gel, eluting with 20% EtOAc in hexane, to afford 2.5 g of 2-(2-amino-5-chloro-phenyl)-4-phenyl-1,1,1-trifluoro-3-butyn-2-ol. ¹ H-NMR (CDCl₃): δ4.63 (br s, 3H), 6.69 (d, J=8.5 Hz, 1H), 7.15 (d, J=2 Hz, 1H), 7.17 (d, J=2 Hz, 1H), 7.35-7.44 (m, 3H), 7.53-7.56 (m, 2H), 7.66 (d, J=2 Hz, 1H). FAB MS M+H=326 m/e.

Step B (+) 6-Chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 12)

A solution of 2-(2-amino-5-chlorophenyl)-4-phenyl-1,1,1-trifluoro-3-butyn-2-ol (2.0 g, 6.1 mmol) and 11.0 g (12.0 mmol) of 1,1'-carbonyldiimidazole in 300 mL of dry THF was stirred under argon at 55° C. for 24 hours. The solvent was removed on a rotary evaporator and the residue was partitioned between 200 mL of ether and 400 mL of water. The layers were separated and the aqueous extracted once more with ether. The combined ether extracts were washed with 2×200 mL 10% citric acid and then with brine before drying over MgSO₄. Removal of the drying agent and solvent provided 1.5 g (70%) of the crude title compound as an oil. Trimration with ether-hexane afforded 875 mg of (±) 6-chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one as a white solid, partial melt at 137°, clear at 147° C. ¹ H-NMR (CDCl₃): δ6.92 (d, J=8 Hz, 1H), 7.30-7.49 (m, 4H), 7.58-7.65 (m, 3H), 8.99 (s, 1H).

Step C 6-Chloro-1-(1S)-camphanoyl-4-phenylethynyl-4-trifluoro-methyl-1,4-dihydro-2H-3,1-benzoxazin-2-one

To a solution containing (±) 6-chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one (2.24 g, 6.37 mmol), 4-dimethylaminopyridine (0.10 g, 0.8 mmol), and (-) camphanic acid chloride (2.07 g, 9.55 mmol) in 60 mL of dry dichloromethane, stirred under argon in an ice bath, was added triethylamine (2.22 mL, 15.9 mmol). The cooling bath was removed and the reaction was allowed to proceed at room temperature. When the reaction was complete by thin layer chromatography (SiO₂, 4% EtOAc in CHCl₃), the solution was diluted with 200 mL of CHCl₃ and washed twice with 10% citric acid, then with brine. Upon drying (MgSO₄) the solvent was removed on a rotary evaporator and the foamy reside was subjected to flash chromatography, eluting with CHCl₃. There was obtained 575 mg of diastereomer I of 6-chloro-(1S)-camphanoyl-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one as an oil, ¹ H-NMR (CDCl₃): δ0.85 (s, 3H), 1.08 (s, 3H), 1.22 (s, 3H), 1.73-1.85 (m, 1H), 1.92-2.08 (m, 1H), 2.50-2.67 (m, 2H), 7.30-7.79 (m, 8H). This was followed by 1.52 g of mixed fractions (diastereomers I and II). Continued elution afforded 680 mg of the slower-moving diastereomer (II) of the title compound which, upon trituration with an ether/hexane mixture, gave clumps of white needles, mp 177°-178.5° C.; ¹ H-NMR (CDCl₃): δ0.83 (s, 3H), 1.12 (s, 3H), 1.23 (s, 3H), 1.73-1.86 (m, 1H), 1.93-2.06 (m, 1H), 2.50-2.63 (m, 2H), 7.38-7.51 (m, 4H), 7.49-7.62 (m, 2H), 7.72 (d, J=9 Hz, 1H), 7.76 (d, J=2 Hz, 1H).

The 1.52 g of isomer mixture from the flash chromatography was dissolved in 75 mL of ether, the solution diluted with 50 mL of hexane, and then seeded with a crystal of isomer II. Slow crystallization afforded an additional 385 mg of isomer II which was recrystallized from ether/hexane to give >96% diastereomerically pure material by HPLC.

Step D (-) 6-Chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one

The crystalline diastereomer(II) of 6-chloro-1-(1S)-camphanoyl-4-phenylethynyl-4-trifluoromethyl-1,2-dihydro-4(H)-3,1-benzoxazin-2-one (53 mg, 0.10 mmol) was dissolved in 8 mL of 2-propanol at 45° C. under an atmosphere of argon. To the solution was added 0.27 mL of a 10% aqueous solution of K₂ CO₃. Stirring was continued for 10 min., by which time all of the starting material had been consumed (TLC, SiO₂, 4% EtOAc in CHCl₃). The solution was concentrated in vacuo and the residue taken up in ether. After washing with 0.1N HCl and brine, the ether solution was dried (MgSO₄), filtered and evaporated in vacuo to an oily solid which was purified by SiO₂ chromatography, eluant 5% 2-propanol in hexane. (-) 6-Chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1 -benzoxazin-2-one was obtained as white needles from ether/hexane, m.p. 178°-179° C.; [α]_(D) 20 =-92.5° (CHCl₃, c=0.0012 g mL-1); ¹ H-NMR (CDCl₃): δ6.87 (d, J=8.5 Hz, 1H), 7.37-7.50 (m, 4H), 7.56-7.63 (m, 3H), 8.60 (s, 1H).

Step E (+) 6-Chloro-4-phenylethynyl-4-trifluoromethyl 1,4-dihydro-2H-3,1-benzoxazin-2-one (Compound 3)

(+) 6-Chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one was prepared from the non-crystalline product of Step C, diasteromer I, in a manner according to Step D: m.p. 178°-179° C.; [α]_(D) ²⁰ =+87.6° (CHCl₃, c=0.0050 g mL-1; ¹ H-NMR(CDCl₃): δ6.87 (d, J=8.5 Hz, 1H), 7.37-7.50 (m, 4H), 7.56-7.63 (m, 3H), 8.60 (s, 1H).

EXAMPLE 6 (-) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one(L-743,726, Compound 37.2) and (+)6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one (L-743,725) Step A 2-(2-Amino-5-chlorophenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol

A solution of bromomagnesium cyclopropylacetylide, was prepared from 23 g of cyclopropylacetylene (0.348 mol) in 250 mL of THF by dropwise addition of 116 mL of a 3.0M solution of ethylmagnesium bromide in ether (0.348 mol) over 1 h. This solution was maintained at 0° C. for 1 h, then at 40° C. for 3 h. To this solution, recooled to 0° C., 15.56 g of 1-(2-amino-5-chlorophenyl)-2,2,2-trifluoromethylethanone (0.0696 mol), was added as a solid, portionwise over 5 min. The reaction mixture was allowed to stir at 0° for 1.5 hours. The reaction was quenched at 0° C. by dropwise addition of 700 mL of saturated aqueous ammonium chloride solution. The mixture was extracted with 2×400 mL portions of ethyl acetate, the combined organic phases were washed with brine and dried over MgSO₄. Removal of the drying agent and solvents left a yellow solid. This material was recrystallized from boiling hexanes (100 mL final volume) to afford 14.67 g of 2-(2-amino-5-chlorophenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol. A second crop (2.1 g) was obtained from concentrating the mother liquors. mp: 153°-154° C. ¹ H-NMR (CDCl₃): δ0.84 (m, 2H), 0.90 (m, 2H), 1.38 (m, 1H), 4.50 (br s, 3H), 6.69 (d, J=8.5 Hz, 1H), 7.13 (dd, J=2.5, 8.5 Hz, 1H), 7.55 (d, J=2.5 Hz, 1H).

Step B (+) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl- 1,4-dihydro-2H-3,1-benzoxazin-2-one (L-741,211)

A solution of 2-(2-amino-5-chlorophenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol (15.00 g, 0.0518 mol) and 41.98 g (0.259 mol) of 1,1'-carbonyldiimidazole in 250 mL of dry THF was stirred under argon at 55° C. for 24 hours. The solvent was removed on a rotary evaporator and the residue was partitioned between 500 mL of ethyl acetate and 400 mL of water. The layers were. separated and the aqueous phase was extracted once more with ethyl acetate. The combined ethyl acetate extracts were washed with 2×200 mL of 2% aqueous HCl, saturated aqueous NaHCO₃, and brine. Drying over MgSO₄, filtration, and removal of the solvent in vacuo provided 16.42 g of the title compound as a solid. Recrystallization from ethyl acetate-hexane afforded 12.97 g of analytically pure (±) 6-chloro-4-cyclo-propylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one as a white crystals. mp: 178°-180° C. ¹ H-NMR (CDCl₃): 0.85 (m, 2H), 0.94 (m, 2H), 1.40 (m, 1H), 6.81 (d, J=8.5 Hz, 1H), 7.37 (dd, J=2.5, 8.5 Hz, 1H), 7.49 (d, J=2.5 Hz, 1H), 8.87 (br s, 1H).

Step C 6-Chloro-1-(1S)-camphanoyl-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one

To a solution containing (±) 6-chloro-4-cyclopropyl-ethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one (12.97 g, 0.041 mol), 4-dimethylaminopyridine (1.02 g, 0.0083 mol), and (-) camphanic acid chloride (14.22 g, 0.06556 mol) in 350 mL of dry dichloromethane, stirred under argon in an ice bath, was added triethylamine (22.84 mL, 0.164 mol). The cooling bath was removed and the reaction was allowed to proceed at room temperature. After 75 min. the reaction was judged complete by thin layer chromatography (SiO₂, 4% EtOAc in CHCl₃), and the solution was diluted with 500 mL of CHCl₃ then washed with 10% citric acid (2X), water (1X), and brine (1X). Drying (MgSO₄), filtration, and removal of the solvent in vacuo left a colorless foam. This material was triturated with 200 mL of boiling hexane. On cooling to room temperature the desired diastereomeric camphanate imide precipitated. The solid was collected on a frit, washed with a little cold hexanes and dried in vacuo to give 7.79g of 6-chloro-1-(1S) -camphanoyl-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one as white crystals. mp: 164°-165° C. HPLC purity: 99.2% @254 nm. ¹ H-NMR (CDCl₃): δ0.77 (s, 3H), 0.86-0.96 (m, 4H), 1.08 (s, 3H), 1.19 (s, 3H), 1.44 (m, 1H), 1.76 (m, 1H), 1.95 (m, 1H), 2.51 (m, 2H), 7.42 (dd, J=2.4,9.0 Hz, 1H), 7.63 (m, 2H).

Step D (-) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl- 1,4-dihydro-2H-3,1-benzoxazin-2-one (L-743,726, Compound 37.2)

6-chloro-1-(1S) -camphanoyl-4-cyclopropylethynyl-4-trifluoromethyl-1,2-dihydro-4(H)-3,1-benzoxazin-2-one (7.50 g, 0.01512 mol) was dissolved in 150 mL of n-butanol at 60° C. under an atmosphere of argon. To this solution was added 10 mL of 1N HCl. This solution was maintained at 60° C. for 72 h. The mixture was neutralized with aqueous NaHCO₃ and the n-butanol was removed in vacuo. The residue was dissolved in 150 mL of THF and treated with 50 mL of 2N LiOH for 3 h at room temperature. This mixture was diluted with ethyl acetate and washed with two portions of water and one of brine. Drying (MgSO₄), filtration and removal of the solvent in vacuo gave a white solid. This material was recrystallized from hot hexane to give 3.43 g of (-) 6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one as white crystals., m.p. 131°-132° C.; [α]_(D) ²⁰ =-84.7° (CHCl₃, c=0.005 g mL⁻¹); ¹ H-NMR (CDCl₃): a δ0.85 (m, 2H), 0.94 (m, 2H), 1.40 (m, 1H), 6.81 (d, J=8.5 Hz, 1H), 7.37 (dd, J=2.5, 8.5 Hz, 1H), 7.49 (d,J=2.5 Hz, 1H), 8.87 (br s, 1H).

Step E (+) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one (L-743,725)

The mother liquors from Step C above were purified by column chromatography on silica gel using 10% ethyl acetate in hexanes as eluant. The pure, undesired diastereomer (a colorless foam) was hydroylzed according to Step D. The enantiomeric benzoxazinone, (+) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, was obtained as white crystals. m.p. 131°-132° C.; [α]_(D) ²⁰ =+84.4° (CHCl₃, c=0.005 g mL⁻¹); ¹ H-NMR (CDCl₃): δ0.85 (m, 2H), 0.94 (m, 2H), 1.40 (m, 1H), 6.81 (d, J=8.5 Hz, 1H), 7.37 (dd, J=2.5, 8.5 Hz, 1H), 7.49 (d, J=2.5 Hz, 1H), 8.87 (br s, 1H).

REVERSE TRANSCRIPTASE ASSAY

The assay measures the incorporation of tritiated deoxyguanosine monophosphate by recombinant HIV reverse transcriptase (HIV RT_(R)) (or other RT) into acid-precipitable cDNA at the Km values of dGTP and poly r(C)·oligo d(G)₁₂₋₁₈. The inhibitors of the present invention inhibit this incorporation.

The assays were carried out in 55 mM Tris (pH 8.2)-30 mM KCl-30 mM MgCl₂ -1 mM dithiothreitol-20 μg of rC:dG₁₂₋₁₈ (Pharmacia) per ml-8 mM [³ H]dGTP (New England Nuclear)-0.01% Triton X-100-50 mM ethylene glycol-bis(β-amino-ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)-1 mg of bovine serum albumin per ml. After 60 min of incubation at 37° C., acid-precipitable material was collected onto glass fiber filters by using a semiautomatic cell harvester. Bacterial cell extracts containing RT were diluted to within the linear range of the assay, and activity was determined in the presence and absence of inhibitor. Purified HIV-1 RT heterodimer produced in E. coli also served as a control. Results are determined as inhibitor concentration to give 50% inhibition (IC₅₀ wt), in nanomoles/liter.

For the double mutant assay (dm), A17 RT was employed in the assay. A17 RT is resistant to various aminopyridones, as described in Nunberg, J. H. et al., J. Virol. 65, 4887 (1991). Results are measured as IC₅₀ dm in nanomoles/liter.

CELL SPREAD ASSAY

Inhibition of the spread of HIV in cell culture was measured according to Nunberg, J. H. et al., J. Virol. 65, 4887 (1991). In this assay, MT-4 T-lymphoid cells were infected with HIV-1 (wild-type, unless otherwise indicated) by using a predetermined inoculum, and cultures were incubated for 24 h. At this time, <1% of the cells were positive by indirect immunofluorescence. Cells were then extensively washed and distributed into 96-well culture dishes. Serial twofold dilutions of inhibitor were added to the wells, and cultures were continued for 3 additional days. At 4 days postinfection, 100% of the cells in control cultures were infected. HIV-1 p24 accumulation was directly correlated with virus spread. The cell culture inhibitory concentration was defined as the inhibitor concentration in nanomoles/liter which reduced the spread of infection by at least 95%, or CIC₉₅.

    ______________________________________                                         SUMMARY OF RESULTS FOR COMPOUND 37.2                                           ______________________________________                                         A. Reverse Transcriptase Assay and Cell Spread Assay:                                  WT          K103N*   Y181C DM    RT-2                                  ______________________________________                                         IC.sub.50 (μM)                                                                       0.002      0.030    0.008 0.085 80.8                                  CIC.sub.95 (μM)                                                                     <0.006(N = 2)                                                                              0.100    <0.025                                                                               0.400 N.D.                                  ______________________________________                                         B. Pharmacological Data:                                                       ______________________________________                                         Rhesus: 1 mg kg.sup.-1 i.v.: t.sub.1/2 = 210 min.                                                              O.B. =                                         10 mg kg.sup.-1 p.o.(methocel: C.sub.max = 4.4 μM @ 2                                                       0.55                                           C.sub.24h = 1.1 μM           (A.U.C.)                                       Protein Binding: 98.0% Normal Human Plasma (HPLC Method)                       ______________________________________                                          *Mutants K103N and Y181C are drugresistant HIV1 reverse transcriptases. D      is the double mutant, as discussed in the reverse transcriptase assay. RT      is the reverse transcriptase of HIV2.                                    

SYNERGISTIC EFFECTS

A. Preparation of HIV-Infected MT-4 Cell Suspension

MT cells were infected at Day 0 at a concentration of 250,000 per ml with a 1:1000 dilution of HIV-1 strain IIIb stock (final 125 pg p24/ml; sufficient to yield <1% infected cells on day 1 and 25-100% on day 4). Cells were infected and grown in the following medium: RPMI 1640 (Whittaker BioProducts), 10% inactivated fetal bovine serum, 4 mM glutamine (Gibco Labs) and 1:100 Penicillin-Streptomycin (Gibco Labs).

The mixture was incubated overnight at 37° C in 5% CO₂ atmosphere.

B. Treatment with Inhibitors

A matrix of nanomolar range concentrations of the pairwise combinations (see Table S) was prepared. At Day 1, aliquots of 125 μl of inhibitors were added to equal volumes of HIV-infected MT-4 cells (50,000 per well) in a 96-well microtiter cell culture plate. Incubation was continued for 3 days at 37° C. in 5% CO₂ atmosphere.

C. Measurement of Virus Spread

Using a multichannel pipettor, the settled cells were resuspended and 125 μl harvested into a separate microtiter plate. The supernatant was assayed for HIV p24 antigen.

The concentration of HIV p24 antigen was measured by an enzyme immunoassay, described as follows. Aliquots of p24 antigen to be measured were added to microwells coated with a monoclonal antibody specific for HIV core antigen. The microwells were washed at this point, and at other appropriate steps that follow. Biotinylated HIV-specific antibody was then added, followed by conjugated strepavidin-horseradish peroxidase. A color reaction occurs from the added hydrogen peroxide and tetramethylbenzidine substrate. Color intensity is proportional to the concentration of HIV p24 antigen.

Calculation of Degree of Synergy

Pairwise combinations of inhibitors (see Table 5) were found to exhibit markedly enhanced inhibition of virus spread, in comparison to each inhibitor alone, or in comparison to merely additive inhibition of each inhibitor. Thus, for example, the pairwise combination of 726 and AZT was found to exhibit markedly enhanced inhibition of virus spread, in comparison to 726 alone or AZT alone, or in comparison to the sum of 726 inhibition and AZT inhibition.

This data was processed as follows: fractional inhibitory concentration ratios (FIC) were calculated according to Elion, et. al. J. Biol. Chem., 208 477 (1954). The minimum sum of FICS, which is the maximum synergy, was determined for various pairwise combinations. Alternatively, an average sum of the FICS is calculated, which is the average synergy. See Table S. These results indicate substantial synergy in the inhibition of virus spread. The smaller the number, the greater the synergy.

                  TABLE S                                                          ______________________________________                                         Pairwise Combinations*                                                                          Average Synergy                                               ______________________________________                                         726 + ddI        0.81                                                          726 + AZT        0.62                                                          726 + 524        0.65                                                          726 + 524 + AZT                                                                ______________________________________                                          524 is L735,524. Other compounds are also defined in Table C above.      

While the foregoing specification teaches the principles of the present invention, with examples provided for the purpose of illustration, it will be understood that the practice of the invention encompasses all of the usual variations, adaptions, or modifications, as come within the scope of the following claims and its equivalents. 

What is claimed is:
 1. A method of inhibiting HIV reverse transcriptase comprising administering to a mammal a pharmaceutically acceptable carrier and an effective amount of a compound of Formula I: ##STR82## or pharmaceutically acceptable salt thereof, wherein: X is halo,X¹ is trihalomethyl, or pentahaloethyl; Z is O;R is: (a) C ₁₋₈ alkyl, unsubsdtuted or substituted with A, and A is halo, C₃₋₆ cycloalkyl, CN, hydroxy, C₁₋₄ alkoxy, C₂₋₄ alkynyl-C₁₋₄ alkoxy, aryloxy, C₁₋₄ alkylcarbonyl, nitro, di(C₁₋₂ alkyl)amino, C₁₋₄ alkylamino- C₁₋₂ alkyl, heterocycle, or arylthio; (b) C₂₋₄ alkenyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A; (c) C₂₋₅ alkynyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A; or (d) C₃₋₄ cycloalkyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A,or a compound of Formula II: ##STR83## or pharmaceutically acceptable salt thereof, wherein: X is halo; X¹ is trihalomethyl; pentahaloethyl; C₂₋₅ alkyl; C₂₋₅ alkynyl; C₃₋₅ cycloalkyl; or aryl; Z is O or S; andR is: (a) C₁₋₈ alkyl, unsubstituted or substituted with A, and A is halo, C₃₋₆ cycloalkyl, CN, hydroxy, C₁₋₄ alkoxy, C₂₋₄ alkynyl-C₁₋₄ alkoxy, aryloxy, C₁₋₄ alkylcarbonyl, nitro, di(C₁₋₂ alkyl)amino, C₁₋₄ alkylamino-C₁₋₂ alkyl, heterocycle, or arylthio; (b) C₂₋₄ alkenyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A; (c) C₂₋₅ alkynyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A; or (d) C₃₋₄ cycloalkyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A.
 2. A method of inhibiting HIV reverse transcriptase comprising administering to a mammal a pharmaceutically acceptable carrier and an effective amount of a compound selected from the group consisting of:(-) 6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, (-) 6-chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, (+/-) 6-chloro-4-(2-cyanophenyl)ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one, (+/-)4-(1-chloro-1,1-difluoromethyl)-4-(2-phenylethynyl)-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one, or (+/-)4-(2-[dimethylaminomethyl]ethynyl)-4-trifluoromethyl-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one,or a pharmaceutically acceptable saIt thereof.
 3. A method of preventing infection of HIV, or of treating infection by HIV or of treating AIDS or ARC comprising administering to a mammal a pharmaceutically acceptable carder and an effective mount of a compound of Formula I: ##STR84## or pharmaceutically acceptable salt thereof, wherein: X is halo,X¹ is trihalomethyl, or pentahaloethyl; Z is O;R is: (a) C₁₋₈ alkyl, unsubstituted or substituted with A, and A is halo, C₃₋₆ cycloalkyl, CN, hydroxy, C₁₋₄ alkoxy, C₂₋₄ alkynyl-C₁₋₄ alkoxy, aryloxy, C₁₋₄ alkylcarbonyl, nitro, di(C₁₋₂ alkyl)amino, C₁₋₄ alkylamino- C₁₋₂ alkyl, heterocycle, or arylthio; (b) C₂₋₄ alkenyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstimted or substituted with A; (c) C₂₋₅ alkynyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstimted or substituted with A; or (d) C₃₋₄ cycloalkyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstimted or substituted with A,or a compound of Formula II: ##STR85## or pharmaceutically acceptable salt thereof, wherein: X is halo; X¹ is trihalomethyl; pentahaloethyl; C₂₋₅ alkyl; C₂₋₅ alkynyl; C₃₋₅ cycloalkyl; or aryl; Z is O or S;R is: (a) C₁₋₈ alkyl, unsubstimted or substituted with A, and A is halo, C₃₋₆ cycloalkyl, CN, hydroxy, C₁₋₄ alkoxy, C₂₋₄ alkynyl-C₁₋₄ alkoxy, aryloxy, C₁₋₄ alkylcarbonyl, nitro, di(C₁₋₂ alkyl)amino, C₁₋₄ alkylamino-C₁₋₂ alkyl, heterocycle, or arylthio; (b) C₂₋₄ alkenyl, unsubstimted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A; (c) C₂₋₅ alkynyl, unsubstituted or substituted withi) A, or (ii) aryl, unsubstituted or substituted with A; or (d) C₃₋₄ cycloalkyl, unsubstituted or substituted with(i) A, or (ii) aryl, unsubstituted or substituted with A.
 4. A method of preventing infection of HIV, or of treating infection by HIV or of treating AIDS or ARC, comprising administering to a mammal a pharmaceutically acceptable carder and an effective amount of a compound selected from the group consisting of:(-) 6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, (-) 6-chloro-4-phenylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, (+/-) 6-chloro-4-(2-cyanophenyl)ethynyl-4-(1,1,1-trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one, (+/-) 4-(1-chloro-1,1-difluoromethyl)-4-(2-phenylethynyl)-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one, or (+/-) 4-(2-[dimethylaminomethyl]ethynyl)-4-trifluoromethyl-6-chloro-1,4-dihydro-2H-3,1-benzoxazin-2-one,or a pharmaceutically acceptable salt thereof. 